Some hardening off is required anytime you change the plant's environment. The greater the change, the more gradual the process needs to be.

Going from in the house to a hoop house is still a big change if only in terms of light exposure and air temps so try not to cut corners. It can end up with lots of wasted effort getting them to this point.

Dave

I agree and disagree. In mid May and beyond when the light is more intense, they will need to be hardened off. I have found that in March and April the plants don't seem to be stressed at all when we move them out of the house and into the high tunnels. Now if it is going to be very sunny and hot, then we harden them off some first. We also like to plant them out on a warm, cloudy day. I will be planting our tomatoes out this week in 2 of our tunnels. We will move them out of the house and plant them directly and water heavily. They seem to take off and not look back. We have been doing this for the last 7 years.

Jay

Advice : new small Hoophouse, Illinois , experienced seed starter. I mostly start annual plants for our wedding barn(cosmos, zinnias etc). I also winter my geraniums and mums. When can I move my established geraniums and mums outside to make room for my baby seedlings under the indoor lights?